U.S.-backed security forces protect government buildings but avoid street clashes. “The situation is chaotic,” says one official.

By Raed Rafei and Borzou Daragahi for the Los Angeles Times

BEIRUT — The Shiite militia Hezbollah today handily took over much of the capital in a dramatic escalation of the months-long confrontation with the Western-backed government, security officials said.

As Hezbollah swept through West Beirut, Lebanon’s security forces, which received more than $270 million in U.S. aid last year, mostly stood by, protecting government buildings but stepping back from the clashes.

“Armed forces from the opposition have taken over Beirut; the situation is chaotic,” said a ranking official of the Internal Security Force. “The army is controlling the sensitive spots like the [parliament] and the residences of main political figures, but the army is not interfering inside the alleys and the streets where the fights are taking place.”

Hezbollah and its allies swept into West Beirut after two days of intense clashes with Sunni fighters loyal to the pro-government Future movement. The clashes were sparked by a government decision Tuesday to outlaw Hezbollah’s fiber-optic communications network and remove an ally as head of security at the country’s sole international airport.

Hezbollah’s allies responded Wednesday by blockading the airport and setting tires on fire. In a major speech Thursday, Hezbollah chief Hassan Nasrallah likened the government’s decision to a “declaration of war” on the Shiite militia and launched an offensive against the neighborhood strongholds and informal militias loyal to the government of Prime Minister Fouad Siniora and the leader of Lebanon’s Sunni community, Saad Hariri.

Sporadic gunfire continued throughout Friday morning and early afternoon after an overnight thunderstorm subsided. But the heaviest fighting appeared to have ended following a routing of the Future movement by Hezbollah and fighters of the allied Amal movement.

Hezbollah and its allies avoided Christian neighborhoods, which remained calm, focusing their offensive on Sunni and mixed Sunni-Shiite districts of the capital. The operation effectively neutered the growing militia of Hariri’s Future movement, which was viewed by security forces and Hezbollah as a potential threat to security.